ON-LINE FILTRATION OF SMEAR REMOVING SOLUTION FROM SMEAR REMOVING TANK

摘要

PURPOSE: To substantially eliminate the clogging of the holes in printed circuit boards by precipitate, by continuously removing deposits by filtration from a desmearing soln. during a desmearing method. CONSTITUTION: The printed circuit boards having drill smears are put into a desmearing tank 12 where manganese dioxide deposits from the soln. The deposits are scavenged toward a return sparger 20 across the bottom of the tank 12 by the flow of the filtrate from a sparger 22. The mixture composed of the soln. and the precipitate is forcibly fed from the tank 12 to a filter system 10. A filter 32 provided with many filter elements remove the deposits and the filtered soln. is returned to the tank 12. The air supplied through an air sparger 24 stirs the soln. and, therefore, the filtered soln. is dispersed to the entire part of the tank 12 and further, the large stagnation of the soln. carrying over the deposits does not arise in any position in the tank 12.